LEAST TWO PRECIPITATORS

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a precipitator for two-stage electrofilters, which precipitator is arranged to receive a through-flow of air to be purified from electrically charged particles present in the air, wherein the precipitator comprises at least two strip-shaped electrode elements arranged at a gap distance from each other, wherein the precipitator is intended to be connected to a high voltage source, the respective electrode elements of the precipitator being connected to different poles of the high voltage source. The invention also relates to an arrangement comprising at least two such precipitators arranged next to each other.

There has been a great focus in recent years to achieve ameliorated indoor air quality, especially with regard to airborne particle pollution in combination with better, i.e. more efficient, use of energy. This has created an interest in the use of electrofilters due to the technology's relatively low pressure drop through filters (so-called precipitators). There is also a growing interest in the use of two technologies in one and the same air purifier, e.g. use of a mechanical filter of a lower filtration class followed by an electrofilter.

BACKGROUND

In the patent specification US 6203600 Bl, a cylindrical precipitator for two-stage electrofilters is described and comprises at least two strip-shaped electrode elements which are wound multiple times with a gap distance from each other around a coil or a ring-shaped element. The method is based on the fact that both strip-shaped electrode elements and flexible strip elements are when forming electrode elements by winding, wherein the flexible strip elements are alternated with the electrode elements during the winding. After winding to a desired diameter and fixation of the electrode elements using for example hot melt glue, the body of the precipitator is turned upside down wherein the flexible strip elements are subsequently removed. If desired, fixation with hot melt glue or an equivalent may be done on the opposite side of the precipitator body. PURPOSE AND CHARACTERISTICS OF THE INVENTION

An object of the present invention is to provide a way to design a cylindrically shaped precipitator for two-stage electrofilters with a larger inlet and outlet surface than that defined by the diameter of the precipitator.

This object is achieved in accordance with the invention by means of a precipitator for two- stage electrofilters intended to be flowed through by air, which is to be purified from electrically charged particles present in the air, and which precipitator comprises at least two strip-shaped electrode elements that are arranged around a centre coil at a mutual gap distance from each other towards a peripheral section, whereby the respective electrode elements of the precipitator are arranged to be connected to different poles of a high- voltage source, where the strip-shaped electrode elements are axially offset in relation to each other such that the precipitator obtains a non-planar shape.

According to a second aspect, the invention relates to a precipitator arrangement comprising at least a first precipitator and a second precipitator as described above, wherein the at least two precipitators are arranged opposite each other, the first precipitator having a ring-shaped element with an open centre arranged to allow an air flow in either direction, and wherein the second precipitator includes an obstruction to force said air flow through the respective electrode elements of the at least a first and a second precipitators.

The precipitator arrangement makes it possible to purify a large air flow with a low pressure drop due to an air purifying effective area extending both orthogonally and axially with respect to the direction of an air flow.

Preferred embodiments of the invention are presented in the independent claims.

BRIEF DESCRIPTION OF THE FIGURES

In the following detailed description, the invention is described with reference to the attached drawings, of which:

Fig. 1 shows a precipitator according to a first embodiment of the invention positioned above a fixture,

Fig. 2 shows a precipitator according to a first embodiment of the invention from the inside, Fig. 3 shows a precipitator partially in sectional view above a fixture, Fig. 4 shows a precipitator according to a second embodiment of the invention from the inside,

Fig. 5 shows a cross-section of a precipitator according to a second embodiment of the invention from the inside,

Fig. 6-7 shows a cross-section of an arrangement with several precipitators,

Fig. 8 is a perspective view of an arrangement with several precipitators,

Fig. 9 shows a cross-section of an arrangement with several precipitators, and Fig. 10 shows a cross-section of an arrangement with several precipitators.

DETAILED DESCRIPTION OF THE INVENTION

The precipitator according to the present invention differs from the precipitator known from the above-mentioned patent document US 6203600 B1 in that its shape is not flat. Specifically, the strip-shaped elements can be arranged so that the shape of the precipitator will be arched, such as, for example dome-shaped or cone-shaped.

Such design has been proven possible to achieve during the winding process in accordance with the description above prior to fixation of the strip-shaped element of the precipitator over a dome-shaped or conical fixture so that the edge sections of the electrode element of the precipitator are pressed against the fixture and then fixed using a type of hot melt glue or an equivalent. The strip-like electrode elements are removed from the fixture, after having been fixated in a non-planar spiral formation.

After fixation, the flexible strip elements may be removed from the fixture. If desired, the electrode elements are fixed by means of hot melt glue or an equivalent on both sides of the precipitator body.

Fig. 1 shows a perspective view of a precipitator unit 1 at an axial distance from a fixture 7, which can be used to give the precipitator unit 1 the desired shape. In the shown embodiment the fixture 7 has a conical shape, but it can of course have another non-planar shape, for example spherical or dome-shaped, to give the precipitator unit 1 the desired shape.

The precipitator unit 1 comprises a bobbin or a ring-shaped element 4 and two strip-shaped electrode elements 2 and 2' which emanate from the ring-shaped element 4 and which are multiply wound with a gap distance "d" between the respective electrode elements around the ring-shaped element 4. The respective electrode elements 2 and 2' are connected to a respective pole of a high voltage source (not shown).

The strip elements 2, 2 of the precipitator may consist of circular rings, where every other ring 2 is connected to one pole of a high-voltage source, for example the plus pole, and every other ring 2' is connected to the other of the high-voltage source's poles, i.e. the minus pole. In the embodiment shown, the strip elements are instead formed by two spiral strip elements which both start from the ring-shaped element 4 of the precipitator and run spirally outwards, one outside the other where one spiral is connected to one pole of a high voltage source and the other spiral is connected to the other of the poles of the high voltage source.

The fixing element 3 is arranged radially to fix the strip-shaped electrode elements 2 and 2' with an essentially constant gap distance "d" between them. Fixing element 3 can in a simple design consist of hot melt glue or an equivalent, but it is also conceivable to arrange comb shaped fixing elements with slots for the electrode elements 2 and 2', the slots being distributed with a gap distance "d" between them.

As can be seen from Figure 2, fixing elements 3, for example in the form of radial strings, can be arranged both on the inside and the outside of the cone/dome-shaped precipitator 1. In addition, fixing elements 3 of different lengths can be arranged to fix the electrode elements 2 and 2', so that they fix all or parts of the laps of electrode elements 2 and 2'. The fixing elements 3 can also be in the form of comb-like components which are arranged radially and which include slots arranged at a distance from each other intended to receive and fix the electrode elements.

An annular collar 6 can advantageously be placed around the outermost laps of the electrode element 2,2'. Preferably, the shape of the precipitator 1 is non-planar in such a way that the surrounding annular collar 6 is axially offset relative to the ring-shaped element 4 in the centre of the precipitator 1.

The body that the individual electrode elements 2,2' form is non-flat, for example cone- shaped or dome-shaped, and constitutes a precipitator unit 1. The electrode elements 2,2' can be made of different materials, but include at least one electrically conducting/ semiconducting part. If the electrode elements 2,2' are made of cardboard and coated with a thin plastic layer, they are preferably provided with moisture protection on their edge parts, whereby reference is made to WO 2013/105885 where a method for applying a moisture protection to electrode elements and a moisture-resistant semi-finished product for the manufacture of precipitators.

In Figs. 3-5, a second embodiment of the precipitator 1 according to the invention is shown, which differs from the first embodiment shown in Fig. 1-2 in that it has a ring-shaped element 4 with a central hole 5. In the embodiment shown in Fig. 1-2, the ring-shaped element 4 preferably has no centre hole, so as not to let air pass inside of the electrode elements.

As shown in Fig. 5, the precipitator body in this embodiment has an inner radius rl and an outer radius r2, the inner diameter defining an area open to the air stream, i.e. a centre hole 5. Between the inner radius rl and the outer radius r2, the strip-shaped elements 2 and 2' can be arranged so that the body they form will be arched and may form part of a dome shaped or a cone-shaped body.

The procedure is based on the fact that during winding (stage 1 of the manufacturing process) strip-like electrode elements 2,2' and flexible strip elements are used, which are placed during winding alternately with the electrode elements 2,2'. The thickness of the flexible strip elements defines a mutual gap distance "d" between the precipitator electrode elements 2.2'. After shaping (against a cone/dome-shaped fixture) and fixing with, for example, hot melt glue, the flexible strip elements are removed and, if desired, the electrode elements 2.2' are fixed with hot melt glue or an equivalent on both sides of the precipitator body.

The coiled precipitator 1 shown in Fig. 5 comprises the ring-shaped element 4 which defines an internal opening of radius rl. The strip-shaped electrode elements 2 and 2', which are connected to the respective pole of the high-voltage source (not shown in the figures), extend from the ring-shaped element 4.

In Figs. 6-10 it is illustrated how several precipitators 1 and 1' can be arranged one behind the other, preferably closely adjacent to each other to form a precipitator arrangement in which the precipitators 1 and 1' are arranged opposite each other with the respective ring- shaped elements 4 facing each other and the respective annular collars 6 against each other. Thereby, a volume V is created inside the assembled precipitators 1, 1'.

Conventionally, for precipitators there has been limitation concerning the possibility to design systems arranged to purify a large volume of air without compromising the efficiency. Since the electrode elements 2 and 2' must be placed at a certain distance from each other to be effective, the air will meet a certain resistance that causes a pressure drop, which is why the total area that the electrode elements 2 and 2' form should be as large as possible. Instead of this area only having an extension in the normal plane in relation to the airflow direction, the non-planar precipitators 1 according to the invention offer that the area can have an extension also in the longitudinal direction, parallel to the airflow direction.

Precipitator arrangements here comprise at least a first precipitator 1 and a second precipitator 1' which are arranged opposite each other, whereby at least the first precipitator 1 has a ring-shaped element 4 with an open centre 5 arranged to allow passage of an air flow in either direction and whereby the second precipitator 1' comprises an obstruction 14 to force said air flow through the respective electrode elements 2,2' of the at least a first and a second precipitator 1,1'.

In Fig. 7, an alternative embodiment is shown where the incoming air enters in partial flows F radially from the precipitators 1,1' and is transported axially in both directions out of the precipitator arrangement after performed purification of the air.

In the embodiment shown in Fig. 8, an obstruction 14 is arranged to cover the centre hole 5 in the ring-shaped element 4 of a precipitator 1 which is arranged at the far end of the precipitator arrangement. In this embodiment, a main air flow F is arranged to enter from one side, left in the figure, through a centre opening (not shown) and to exit in partial flows F (see Fig. 9) through the strip elements of the various precipitators 1. The obstruction 14 can thus consist of a circular disk with a radius corresponding to the radius rl of the ring- shaped element 4.

As indicated in Fig. 8, the precipitator arrangement may advantageously be arranged inside a surrounding channel 10 with a larger cross-sectional area than the individual precipitators 1 and for example with a multi-sided cross-section such as rectangular, whereby impure air is transported on one side of the precipitators, either inside or outside, and the purified air after passing between strip elements of a precipitator is transported on the other side.

In an alternative (not shown) embodiment, the outer radius r2 of the precipitators can be larger at one axial end, where a major part of the air is to travel inside the precipitators, and be smaller at the opposite axial end, where a major part of the air instead must travel outside the precipitators. Thus, in the case where the incoming impure air is admitted to the inside of the precipitators, the precipitators may have a decreasing outer radius as more air is purified and passes outside the precipitators but inside the duct 10 until all the air has been purified at the far end of the duct 10.

In the embodiment shown in Fig. 9, the obstruction 14 is instead arranged to cover the surface radially inside the annular collar 6 of the precipitator 1 which is arranged at the far end of the precipitator arrangement, where the obstruction 14 can consist of a circular disc with a radius corresponding to the radius r2 of the annular collar 6.

A rotation device (not shown) is advantageously provided to rotate the precipitator arrangement. In the embodiment shown in Fig. 8 and 10, a tub 11 is arranged under the precipitator arrangement in which a lower part of the precipitators 1 may be received, the tub 11 being arranged to contain a washing liquid 12 for purifying the precipitators 1 while they are rotated by means of the rotation device. An outlet hole 13 can be arranged in the tub 11 to lead away used washing liquid.

MODIFICATIONS

The precipitator's electrode elements can suitably be designed in an already known manner using e.g. cardboard or suitable plastic. Advantageously, the electrode elements can be made of a very high-resistance or antistatic material or be coated with such material that is also moisture and water resistant.

Of course, shaping of the precipitator need not result in a dome or conical body. A different shape may be desirable with regard to, for example, the appearance of the air purifier if the precipitator is placed as a visible element.

Advantageously, the precipitator can be surrounded by a ring-shaped element. For the sake of stability, functional radial spokes can be arranged starting from either the ring-shaped element or from the annular collar. There is nothing preventing the ring-shaped element from being provided with a centre opening if desired. This could, for example, be beneficial when purifying the precipitator.

It has also been found that a low conical or dome-shaped precipitator can be achieved by heating the already hot-melt assembled planar spiral precipitator body over a suitable fixture.